This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. To examine the effects of smoking cessation and smoking resumption on insulin resistance and its markers, cardiovascular risk factos, changes in body composition and fat distribution, and changes in the metabolism of body fuel substrates in humans.